1. Field of the Invention
This invention relates to biodegradable carriers. More particularly, this invention relates to cellulosic carriers and methods of producing these carriers. The cellulosic carriers of this invention are used primarily for pesticides such as herbicides, insecticides, larvacides, rodenticides and diluents for biological agents.
2. State of the Art
It is well known that cellulose materials are good absorbents, and their use is desirable because they are biodegradable. Cellulose materials such as wood shavings or sawdust, rice hulls, corncobs, pecan shells and peanut shells can be densified by a compacting or a pelletizing process. When the final product is to be used as an absorbent, lower density and higher surface area is desirable. U.S. Pat. Nos. 5,062,954 and 5,064,407, both assigned to The Andersons of Maumee, Ohio, the present assignee, set forth processes for making absorbent products from these materials with corncobs being a preferred material.
Approximately 60% of a corncob is made up of hard woody ring or grit. Corncob grit granules have long been used for a wide variety of pesticide carriers. A good listing of some 37 pesticides by their primary name and also various trade names, which pesticides have been formulated on granular grit carrier, is presented in Table 140 of the publication PHYSICAL PROPERTIES, CHEMICAL PROPERTIES, AND USES OF THE ANDERSONS' CORNCOB PRODUCTS published by The Andersons of Maumee, Ohio. For example, diazinon is currently being used in the eradication of fire ants. Another well known pesticide is known as Dursban.RTM..
It is also known that the lighter corncob components, which include coarse chaff, fine chaff and pith which constitute about 40% of the corncob by weight, tends to have a higher release rate than the hard woody ring when used as a carrier. This fact is utilized in the teachings of U.S. Pat. No. 4,563,344 assigned to The Andersons. This patent teaches making an agglomerated carrier having a quicker releasing component and a slower releasing component of the soft corncob components and the hard corncob components respectively which are impregnated with different pesticides which are to be released at different rates.
There has been no attempt in the art to produce a dense cellulose carrier having a high resistance to attrition in a granular product in a variety of size ranges.